Release 0.2.7 for VNX and Unity support.

Add support for new VNX driver and Unity Manila driver.

Details changes below:

• [API-90] align behavior of 'get_iscsi_port'
• [API-84] Enable VNX File resources from VNXSystem
• [API-89] Change emcpywbem to pybwem
• [API-78] Component test for VNX Lun create/delete
• [API-85] Default VNX list property to empty.
• [API-81] Add perf counter support for VNX LUN.
• [API-82] Add perf counter support for VNX SP.
• [API-86] SMP name in use exception
• [API-83] Add available IP in VNXSystem
• [API-80] Convert lun_list in cg from id to object
• [API-79] change delete_image to remove_image
• [API-76] Avoid heart beat if login failed
• [API-77] component test framework and CI
• [API-72] Add brief document.
• [API-75] Add Mirror view's Ownership
• [API-22] Use delete instead of remove.